A hybrid vehicle including an engine that is operated by a combustion energy of fuel and an electric motor that is operated by an electric energy has been variously developed. The engine and the electric motor serve as power sources in a driving state of the hybrid vehicle. The hybrid vehicle has lately attracted the attention because noise and air contamination, for example, are avoidable by the electric motor mainly serving as the power source in a normal driving state of the hybrid vehicle. In addition, disadvantages of an electric vehicle, specifically, difficulties In a sudden acceleration, a high-load driving, and a high-speed driving caused by an insufficient mileage by one charge of battery or less torque generation, for example, may be eliminated by a combination use of the engine operated by the combustion energy.
According to the aforementioned hybrid vehicle, in order to selectively use the engine and the electric motor depending on a driving state of the hybrid vehicle, the hybrid vehicle includes plural driving modes in which each of the engine and the motor operates differently. Specifically, the plural driving modes include an engine driving mode in which the hybrid vehicle is driven only by the engine as the power source, a motor driving mode in which the hybrid vehicle is driven only by the electric motor as the power source, and an engine and motor driving mode in which the hybrid vehicle is driven by both the engine and the electric motor as the power sources, for example. The driving mode of the hybrid vehicle is automatically switchable depending on a mode switch condition that is specified beforehand, i.e., a power source map, for example, where the driving state of the hybrid vehicle including a vehicle speed and an accelerator operation amount serves as a parameter.
According to the aforementioned hybrid vehicle, however, in a case where either the combustion energy or the electric energy disappears, one of the power sources using the energy that disappears is inhibited from operating. Thus, even when the other of the power sources is operative, the driving performance of the hybrid vehicle may be deteriorated.
Therefore, a hybrid vehicle disclosed in JP10-28302A (which will be hereinafter referred to as Reference 1) includes a residue determining means for determining whether or not a total energy residue of an engine and an electric motor or an energy residue of the engine is equal to or smaller than a threshold value, and a mode switching means for switching each of the operating conditions of the engine and the electric motor to a mileage increase mode in which a mileage of the hybrid vehicle increases.
In addition, an automated manual transmission (which will be hereinafter referred to as an AMT) obtained by attaching an actuator to a known manual transmission is known to automatically perform a gear shift operation including an engagement/disengagement of a clutch and a gear shifting based on an intention of a vehicle driver or a vehicle state. According to the ATM, in a state where the clutch is in a disengagement state during the gear shifting, a torque from the engine (an engine torque) is not transmitted to wheels. Thus, even in a case where the vehicle driver desires or requires accelerating the vehicle, the acceleration of the vehicle is zero, which leads to a loss of acceleration feeling (a torque drop).
Therefore, according to the hybrid vehicle including the engine and the electric motor as the power sources, a gear shift assist is performed so as to apply a driving torque of the electric motor to the wheels as an assist in the disengagement state of the clutch. Then, the loss of acceleration feeling, for example, is avoidable.
Further, in a case where a request torque is equal to or greater than the engine torque that may be output during the driving state of the vehicle or even the request torque is smaller than the engine torque that may be output during the driving state of the vehicle, a driving assist where the driving torque from the electric motor is applied to the wheels as the assist of the engine torque is conducted for the purpose of energy saving.
According to the hybrid vehicle disclosed in Reference 1, when the energy residue is equal to or smaller than the threshold value, each of the operating conditions of the engine and the electric motor is brought into the mileage increase mode In which the mileage of the vehicle increases. The driving assist and the gear shift assist are still continuously performed.
In addition, according to the hybrid vehicle including the AMT, the gear shift assist where the driving torque of the electric motor is applied to the wheels in the disengagement state of the clutch during the gear shifting is impossible in a case where the energy residue of the electric motor (i.e., an SOC value of the battery) is reduced. Thus, a gear shift feeling may be drastically deteriorated (a loss of acceleration feeling or a gear shift shock, for example).
A need thus exists for a control apparatus of a hybrid vehicle which is not susceptible to the drawback mentioned above.